Aquatic species are exposed to chemical pollutants that are discharged into rivers, lakes and estuaries or those leaching out of neighboring dump-sites. Many of these pollutants affect the health of fish by enhancing the incidence of diseases and, in extreme cases, lead to their death. We propose to utilize a number of assays, both in vitro, and in vivo, to determine the effects of the aquatic contaminants on some of the immune responses of fish. Poeciliopsis lucida, a small viviparous fish which delivers large broods with short latency periods between birth, can be easily maintained in the laboratory. An isogeneic clone of this fish will provide genetic stability, which would lead to the increased reproductability of the results. This fish has already proved useful in laboratory studies because of its enhanced sensitivity to carcinogens, short latency period of tumor development and lack of spontaneous tumors. The main objective of this proposal is to develop Poeciliopsis lucida as a system for evaluating the impact of chemicals emanating from Superfund sites on the health of fish. The chemicals proposed for this study are Cd2+, Ni2 and methylmercuric chlorides, and Aroclor 1254 which is a mixture of polychlorinated biphenyls. At first, normal immune functions of macrophages (m0) (as measured by H2O2 production, mobility and phagocytosis), tumoricidal activity of m0 and of nonspecific cytotoxic (NC) cells, host susceptibility to infections and to tumor formation will be determined. Then, the effects of in vitro pretreatment with the chemicals under study or their mixtures on the functional activities of m0 and the tumoricidal activities of m0 and NC cells, will be evaluated. This will be followed by determination of the effects of in vivo exposures of fish to chemical(s) on the same endpoints as before. The last aim is to compare the effects of water and sediment from a contaminated aquatic area on Poeciliopsis lucida immune cell functions and susceptibility of fish to infections and cancer with those caused by chemically contaminated water and sediment prepared in the laboratory.